The field of mechanical circulatory support has expanded immensely over the last few decades. Survival has reached 10 years for patients implanted with axial flow blood pumps. (example: the Jarvik 2000 and the HeartMate II). In addition to the axial flow models, centrifugal flow rotary blood pumps such as the Heartware and HeartMate3 have been implanted in thousands of patients over the past decade. In the years ahead, many of these patients will reach survival beyond a decade. The available flow and pressure has been sufficient, with modest power requirements low enough that a battery weighing only 1 Kg will power the blood pump for more than 8 hours. Durability of the devices has been excellent using blood immersed ceramic bearing designs. This has all but eliminated the need for shaft seals with the exception of temporary catheter mounted miniature pumps intended to be used up to a few weeks, and in one model implantable LVAD. Several pumps using partial or full magnetic suspension of the impeller have been developed. These include the Heartware and the HeartMate 3.
U.S. Pat. No. 5,399,074 (Kyocera) discloses an extracorporeal bypass pump, one embodiment of which includes channels behind the impeller shroud to allow blood to wash behind the shroud and return to the primary blood flow path.
But despite major advances, some important complications continue to occur in all present VADs. These include, 1) infection, 2) formation of thrombus within the pump, 3) embolic and hemorrhagic strokes, and 4) blood damage.
Olsen et al. U.S. Pat. No. 4,688,998 (FIGS. 10 and 11) discloses double suction centrifugal blood pumps but the design requires two inflow conduits. This makes several prior art designs that use them unsuitable because they are too large to implant within the pericardium. U.S. Pat. No. 5,938,412 discloses another example of a double suction blood pump configuration. In this case there is one inflow and two outflow conduits exiting the housing.
U.S. Pat. No. 9,835,158 discloses a centrifugal pump having two “back to back” rotors constituting a double suction design with a bifurcated inflow tube. In the embodiment shown in FIG. 1, the bifurcation requires a large housing to accommodate duel inflow tubes downstream of the bifurcation that pass through the motor. This results in a complex pump that is too large to implant in the apex of the left ventricle and requires an abdominal pump pocket to fit it in the body. The same is true of the other embodiments that utilize motor and magnetic levitation windings surrounding the pump impellers. In the embodiment shown in the '158 patent, FIG. 3, a blood inflow tube with side holes passes through the magnetically levitated rotor, thereby supplying blood to the inflow of both “back to back” impellers. But the use of side holes can cause hemolysis, and they should be avoided where possible. The single inlet double suction design of the present invention allows the blade shape and flow channel to be nearly identical for both sides of the impeller. Without using side holes for the flow or a bifurcated inflow tube the flow is divided into two streams, with approximately 50% passing across each face of the impeller, and the flow re-forms a single stream as the flow enters the volute.